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"Weak Links and Sorting Eggs"

HammerSandwich

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aka Roger Skoff writes about the best way to approach improving your system at Positive Feedback. Ignore the analogy between eggs & audio systems, and the lesson boils down to this:
Even with extreme bass response available to you, unless your room is big enough (the room here being the “smallest hole”), you won’t be able to hear it. In any room, the lowest frequency that can be propagated is limited by the longest dimension of the room and its wavelength is equal to twice that longest dimension. To find out what your room’s lowest bass frequency is, just multiply the room’s longest dimension (18 feet, for example) by 2 (to recognize that it’s only half a wavelength) and divide it into 1120 feet per second, the nominal speed of sound in air at sea level.
I suppose that's why IEMs are inaudible below several kHz. :rolleyes: Apparently, neither the author nor PF's editorial staff could spend the few seconds' thought needed to realize this before they published... :facepalm:
 

nerdstrike

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That must be why car chumps stand outside their car when running their stereos to max. Infinite room size amiright?
 

egellings

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I suspect that the IEM simply pressurizes the ear canal, which acts as a conduit for the pressure. As a result, the canal does not do much to the sound in the way that a room would to a speaker's efforts. As an analogy, if the room were like a waveguide, then the ear canal would be like a short piece of wire.
 

DVDdoug

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I've head that "theory" before. In fact a physicist once told me that those guys with the boomy car stereos can't hear it inside the car. But there was something else going-on and we didn't have time to discuss it.

There must be some semi-valid theory behind this and MAYBE it has something to do with "propagation". I don't know what the theory is, plus I'm not a physicist, so I can't argue the theory...

I only know from experience that it's wrong. (And I know a little about standing waves.) I can hear bass in my headphones and in the car. And logic tells me if I could seal my head inside a speaker (or if I cut a hole and sealed my ear against the speaker), the pressure waves would move my eardrum and I could hear the bass...

And under certain conditions I can feel "zero Hz" pressure on my ears, unrelated to room size.
 

egellings

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If you look at the distance between the IEM's diaphragm and the ear drum when the IEM is inserted into the ear, It's a tiny fraction of a wavelength of even a high-pitched sound.
"0Hz pressure" is the prevailing barometric pressure?
 

EJ3

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That must be why car chumps stand outside their car when running their stereos to max. Infinite room size amiright?
I thought that they did that so that when their bass pressurized the vehicle, that they would look cool being hit by the shattering side window glass.
 

briskly

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There must be some semi-valid theory behind this and MAYBE it has something to do with "propagation".
Perhaps some confusion with electromagnetism? This is one point where comparing acoustic to EM waveguides does not work. An electromagnetic waveguide rejects the zeroth mode, which starts from DC. Of course, you can sustain a pressure difference in an airtight chamber.

I suspect that the IEM simply pressurizes the ear canal, which acts as a conduit for the pressure. As a result, the canal does not do much to the sound in the way that a room would to a speaker's efforts. As an analogy, if the room were like a waveguide, then the ear canal would be like a short piece of wire.
A fair amount of canal behavior can be decently approximated with a transmission line analogy. The canal length resonances are still a hot topic wrt circumaural and in-ear headphone measurements. You can see the first half-wave resonance when looking at measurements of in-ear headphones, sometimes even the second.
 

mansr

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I thought that they did that so that when their bass pressurized the vehicle, that they would look cool being hit by the shattering side window glass.
I wonder what this guy heard?
_110162976_el5sbguwsaax3tz.jpg

A driver caused an explosion in his car when he lit a cigarette after spraying air freshener.
He used "excessive" amounts of the aerosol scent before sparking up, according to firefighters.
Gas from the spray ignited, blew out the windscreen and windows and buckled the doors but the man escaped with only minor injuries.
 

MRC01

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The bass formula in that article is demonstrably incorrect. My listening room's largest dimension is 16.5' L-R. By his formula I should only be able to hear bass down to 33 Hz in this room. But I can clearly hear 25 Hz which is the lowest my speakers will reproduce. And REW freq sweeps show smooth response.

That car reminds me... back in college in the 80s one of the guys on my dorm floor had a hatchback like that with a ludicrously loud stereo (ludicrously loud is even louder than ridiculously loud). Dual 15" woofers in the hatchback, he had a beefed up alternator & battery to power the stereo. He had blown out the rear glass and replaced it with heavier duty glass that could withstand the vibration. He wore 30 dB workshop earmuffs while playing that stereo. He won several local car stereo competitions in the "loudness" category. You could definitely hear the low bass inside the car, though it was masked by one's skull and eyeballs vibrating, even through heavy duty earmuffs.

The only thing I've ever heard that was louder than his car stereo was working on the deck of an aircraft carrier during flight ops. There, I wore 30 dB foam plugs with 30 dB muffs over them, and it was still painfully loud.
 

egellings

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I look at those ludicrous car stereos and wonder, why? Why on earth? It's no longer serving music anymore. Maybe it's some skinny guy driving around a gym parking lot tying to impress the membership.
 

MRC01

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I don't doubt there are nearly as many different reasons as there are loud car stereos. In the case of the guy I mentioned above, it was a form of jokester fun, just a hard working stressed college student looking for a way to blow off steam. The fact that it was an annoying nuisance added to his fun, in a juvenile way. Not much different from guys who put loud pipes on their motorcycles and cars.
 

EJ3

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I don't doubt there are nearly as many different reasons as there are loud car stereos. In the case of the guy I mentioned above, it was a form of jokester fun, just a hard working stressed college student looking for a way to blow off steam. The fact that it was an annoying nuisance added to his fun, in a juvenile way. Not much different from guys who put loud pipes on their motorcycles and cars.
There is loud (Loud pipes DO save lives [pipes that, if you were a blind person crossing the street, they would cause them to wait until whatever has those pipes went by]) and then there is excessively loud. My back yard is a series of marsh & creeks that go to a harbor. About 3 miles away is an interstate bridge. I can just barely here the sirens of emergency vehicles crossing that bridge when I am sitting on my dock, but sometimes I here someone's exhaust system more clearly than the sirens. That is definitely excessively loud. Along with when I can hear CLEARLY the exhaust of the vehicle idling next to me in traffic when the windows of my Lexus are closed and I am listening to the Mark Levinson stereo (yes, I know what happened to him & the company that bears his name, but the system in the Lexus is still pretty good) at a not so moderate volume.
 

EJ3

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What happened to Levinson & Co.?
Without going into too many details, Wikipedia gives this synopsis:
Mark Levinson worked as the bassist for five years (1966–1971) for jazz pianist Paul Bley and played with other renowned jazz musicians of the period.[1]

In 1972, Levinson founded Mark Levinson Audio Systems (MLAS, Ltd.) in New Haven, Connecticut. He ran MLAS from 1972 to 1980, during which time he created products such as the LNP-2 preamplifier. He also invented the concept of high-end car sound in 1979.[citation needed]

However, by 1980 MLAS was in financial trouble. Levinson then asked Sanford Berlin, a retired executive in the audio industry, to invest in MLAS and to aid in the management of the company. Berlin personally invested $480,000 in the company and persuaded several others to invest an additional $300,000.[citation needed]

In the summer of 1984 Levinson left MLAS and founded another company to produce audio equipment, Cello Ltd. Levinson became president and one of the three directors of Cello. MLAS launched a lawsuit attempting to prevent Levinson from working in the audio industry for the rest of his life, on the grounds that he was a "walking trade name" who could "diminish the value of their asset."[2]

Levinson won the case in 1986 but lost the right to use his name as a trade name on an audio product.[3] For this reason, since several years before the lawsuit, "Mark Levinson" branded audio products have had no relationship to the brand's founder; the "Mark Levinson" brand name has been and continues to be an intellectual property wholly owned by Harman International. In resolving the case, the Second Circuit Court of Appeals wrote a 25-page decision that outlined the rights of entrepreneurs who use their own name as the name of a company.[citation needed] Levinson himself has continued to work in the industry, creating several new companies.

Levinson ran his second company, Cello Ltd., from 1984 to 1998. With Cello, Levinson created high-priced models such as the Audio Palette.[citation needed] In 1999, Levinson founded Red Rose Music, an audio company with its own New York retail store on Madison Avenue. The business model of Red Rose was to create compact, affordable products with very high-quality sound.[citation needed]

In 2007, Levinson moved to Switzerland and used his consulting revenue to finance the founding of Daniel Hertz S.A., a high-performance audio equipment and audio software company with a holistic approach, that considers the quality of recordings an important part of the playback system.[4]

EJH: My knowledge of it is that Levinson did not exactly leave voluntarily: Berlin went in with intent & organized the other investors to kick Levinson out.
 
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